Mercury-tube switch



1,642,932 I. E. M CABE MERCURY TUBE SWITCH Sept. 20, 1927.

Original Filed July 9, 1923 IN VEN TOR.

IRA EM CABE' BY ad a, M

ATTORNEYS.

Patented Sept. 20, 1927.

UNITED STATES nu a. means, or CHICAGO, rumors.

MERCURY-TUBE SWITCH.

Original application filed July 9, 1923,

This invention relates to improvements in electric switches and more particularly to mercury tube switches the operation of which is adjustably controlled by temperature and electricity combined, and this application is a divisional ap lication of my pending application, Serial uly 9, 1923.

It is an object of this invention to construct a mercury tube switch with two branches providing wells in which the contacts are located and are adapted to be covered and uncovered by the mercury to make and break the circuit therethrough and with bulbs or enlarged extensions in the branches above the mercury containing inert gases with an electric heating unit in each branch and a metal float in the main portion which latter is surrounded on the exterior by a magnet adapted to co-operate with the metal core. Current passing through the heating unit expands the gas in that bulb and depresses the mercury to break the circuit b uncovering a contact in that branch or c ose the circuit by raising the level of the mercury and covering a contact in another branch or both. The metal float surrounded by the exterior magnet may be raised or lowered in the mercury by the magnet and will adjustably control the level of the mercury in the tube and may make or break the circuitthrough the mercury to the contact or may be operated in conjunction with the heating unit to adjust the time of operation thereof.

This device is of advantage wherever it is desirable to provide an independent time control for the actuation of the 0 eration of the switch such as in battery c arging devices, sign flashing, voltage regulation, and safety devices in an electric current to break the circuit at a definite load as well as in connection with motor starting switches.

While the preferred forms of this invention are illustrated upon the accompanying sheet of drawings, it is to be understood that minor detail changes may be made without departing from the scope thereof and the application of this invention is not limited to the uses described herein.

In the drawing:

A view part1 in central vertical section through an em dymen't of this improved switch, with a wiring diagram, is illustrated.

The drawing illustrates a simple form of 0. 650,233, filed Serial No. 650,283. Divided and this application fled October 8, 1926. Serial No. 139,798.

this invention employing a vertical tube 1 provided with oppositely disposed branches 2 and 2 leading into bulbs 3 and 3 and each having projections 4 and 4 provided with wells 5 and 5" into which project the contact 7 and 7. An electric heating unit 8 1s suspended in the bulb 3 having its contacts 9 an 10 passing through the top of the bulb and a similar heating unit 8 is suspended in the bulb 3* having its contacts 9 and 10 passing through the top of the bulb. An iron or other magnetic sensitive metal float 11 which will not form an amal gain is arranged within the vertical tube 1. Mercury 12 is introduced in the tube until the mercury supporting the float passes into the horizontal rojections 4 and 4 and fills the wells 5 a-nd ti and its level is about the center of said projections. Inert gases are introduced into the tube land bulbs 3 and 3 above the level of the mercury and the tube and bulbs closed. A magnet 13is arranged about the exterior of the tube 1 in such a position as to embrace theupper portron of the float 11. If the magnet is an electnc magnet it is preferably stationary as the energizing thereof will draw the float upwards. If the magnet is a fixed one it is provided with a sliding movement over the tube 1 so that its upward movement will draw the float 11 upward and its downward movement will draw the float downward.

The drawing shows the mercury tube switch with the parts in normal position and the circuit closed through the mercury 12 from contact 7 to contact 7 which is the circuit designed to be controlled by said switch. The operating elements of the switch are the heating units 8 and 8* and the adjustable time control for the actuation of the operating element is the magnetically adjustable float 11.

As the current passesthrough a heatin unit it raises the temperature within the bulfl containing it, expanding the gases therein, and depresses the level of the mercury below it in the adjacent branch until its level is below the bottom of the horizontal projection thereof. The cohesive property of mercury causes that in the horizontal ro- 105 jection 4 or 4- to cling to that in the we 1 5 or 5 and then break with a snap action to follow the main body of mercury down branch 2 or 2 as its level is depressed below the bottom of the horizontal projection 110 and with the inert gas filling the said projection there is little or no arcing when the circuit is broken with the contact through the mercury remaining in the well 5 or 5.

The time of actuation of the operating heat units 8 or 8 depends upon the level of the mercury in the projections 4 or 4F, and the amount of current passing through the heat unit the higher the level the longer time or more current it will take to break the circuit.

The level of the mercury in the projections 4 and 4 before either heat unit is energized depends upon the position of the float 11 within the mercury 12. When the magnet 13 is an electro-magnet and is de-energized or is a fixed magnet in normal position and the heat units de-energized the level of the mercury in the projections at, 4 and tube 1, and the relation of the float to the mercury 12 are normal, it will take a, definite amount of current to raise the temperature of a heat unit to expand the gas in its bulb sufficiently to depress the level of the mercury enough to break the circuit at the adjacent contact in a definite length of time. The energizing of the electro-magnet or the raising of the fixed magnet 13 draws the float upward causing it to displace less of the mercury 12 and lower the normal level of the mercury in projection 4-, hand tube 1 which will decrease the length of time required for the same amount or: heat in a bulb to break the circuit at its adjacent contact. An increase in voltage of the current passing though the electro-magnet will continue to draw the float 11 upwards decreasing the time for the same amount of heat in a bulb to break the circuit and conversely as the voltage through the electro-magnet decreases the float 11 approaches its normal displacement of mercury and the time of operation approaches the normal also. A fixed magnet may be caused to slide upon the exterior of the tube 1 by manual or any desired mechanical means, such as a pressure controlled Bourdon tube, and as it moves upward from normal it will raise the float upward lessening the time the same amount of heat in a bulb will break the circuit through its adjacent contact, Lowering the fixed ma net below normal on tube 1 wilbcause the oat 11 to descend lower into the mercury 12 and consequently dis place more mercury, raise the level of the mercury in tube 1 and project-ions 4 and 4 and increase the time beyond normal for the same amount of heat in a bulb to break the circuit through its adjacent contact.

The wiring shown in diagram in connection with this form of tube switch illustrates the application of this invention as a safety device or cut-out in a three phase circuit to prevent under voltage or single phasin A, B, and C indicate the service lines,

and C being 220 volts and B 110 volts. In this form contacts 5 and 5* are connected by conductors D and E, respectively, to a magnetic switch S'connected to close the service line circuit to the source of current as long as it is in circuit DE and to break the service line circuit when DE is broken. The solenoid 13 is arranged in shunt circuit by conductors F and G with the 220 volt line C and 110 volt line B so that under normal conditions the plunger 11 is held within the mercury 12. The heating elements 8 and 8, the latter of twice the resistance of the former, are arranged in series by conductors H, I, and K between the 220 volt line G and 110 volt line B and also connected by conductor L from the 220 volt line A. A drop in voltage or the blowing out of a fuse in any one of the three service lines A, B, or G, will disturb the balance of the mercury in the tube to break the circuit through the magnetic switch and discontinue the current through the service lines.

What I claim is:

In an electric switch, a sealed mercury tube having three vertical branches connected by a horizontal passage, the outer branches having horizontal projections provided with depending wells, electric contacts entering the wells, mercury within the tube normally at a height to enter the projections and complete a circuit between the well contacts, gases above the mercury in each branch, electric heating units in the space above the mercury in the outer branches, electric connections for the heating units passing through the walls of those branches, which, by the energizing of both heating units maintains the level of the mercury constant and the circuit complete between the well contacts and the de-energizing of one allows the gas in that branch to contract and the level of the mercury to rise breaking the circuit of the well contacts in the other outer branch, a metal float in the third branch, a solenoid arranged wholly on the outside of that branch which when energized maintains the float immersed in the mercury to complete the circuit between the well contacts and upon de-ener ization withdraws the float to lower the level of the mercury and break the said circuit.

IRA E. McCABE. 

